The present invention relates to photocatalytic compositions and in particular, but not exclusively, to photocatalytic cleaning compositions, intended to reduce the frequency and/or effort of cleaning; and to methods employing such compositions. References will be made herein to cleaning compositions and/or to compositions which are effective in combating malodours and/or soils and/or microorganisms, these being preferred compositions, but descriptions and definitions which follow are applicable also to compositions intended for other purposes.
Cleaning compositions of the invention are of particular interest for cleaning surfaces such as ceramic tiles, sinks, baths, washbasins, toilets, worksurfaces, ovens, hobs, carpets, fabrics, floors, painted woodwork, metalwork, laminates, glass surfaces and the like.
Cleaning compositions intended for general and for specific uses are well known in the art. Such compositions, when liquid, will commonly comprise one or more surfactants, to loosen and/or disperse oily deposits and to dissolve water soluble materials. These cleaning compositions may include one or more of solvents (including water), thickening agents, abrasive particles, bleaching agents, disinfectants/antibacterial agents, perfumes, waxes or other polishing agents, preservatives, colouring agents and like additives. The liquid formulation provides a vehicle for the removal of insoluble particulate matter and builders and suspending agents are often included in the compositions to facilitate this process. These prior art compositions are, to a greater or lesser extent, effective in removing soils, usually organic soils, from surfaces and in preventing their redeposition during the cleaning process. However, re-soiling of the surfaces after cleaning is an inevitable and continuous process.
Thus, domestic and other surfaces are continually dirtied or soiled by various means including, for example, soiling resulting from the preparation of food, contact by people and domestic pets, deposition of oily deposits and of airborne materials. Not only are these and like soils aesthetically displeasing, they may also have deleterious effects on health. The soils may contain allergenic material such as pollen, dust mites, dust mite droppings, cat and other animal allergens and furthermore may include harmful or toxic materials derived from adjacent or nearby industrial, horticultural or agricultural processes. Deposited soils may also harbour and give sustenance to pathogenic microorganisms or might include residues of human or animal faeces or urine. It is therefore important that these and like deposited soils are removed from surfaces efficiently and frequently.
Cleaning of surfaces is therefore a frequent and often time consuming requirement and is inevitably regarded as an unpleasant chore. There is a need for means to reduce the frequency of cleaning, and desirably also to facilitate the removal of soils deposited on surfaces. It will be appreciated that known, conventional, cleaning compositions have no effect on soils deposited on the surfaces after the cleaning process until such time as the cleaning process is undertaken again. The present invention therefore seeks to provide cleaning compositions which, after the cleaning process, are effective to reduce the required frequency of cleaning and/or to facilitate the removal of deposited soils.
It is an object of embodiments of the invention to provide a composition showing improved photocatalytic action.
In accordance with a first aspect of the present invention there is provided a composition which comprises in admixture a photocatalytic material or a precursor to a photocatalytic material, and a sensitiser which acts to absorb visible or ultra violet or infra-red radiation and enhance the photocatalytic action of the photocatalytic material.
It is an object of embodiments of the invention to provide a cleaning composition which, in addition to combating existing malodours and/or soils and/or undesired microorganisms when applied to a locus, for example a surface, combats further malodour compounds and/or soils and/or undesired microorganisms, after its application to a locus.
In accordance with a second aspect of the present invention there is provided a composition comprising a photocatalytic material able to combat malodours and/or soils and/or undesired microorganisms at a locus, or a precursor to such a photocatalytic material, and a sensitiser which acts to absorb visible or ultra-violet or infra-red radiation and improve the efficacy of the photocatalytic material in combating malodours and/or soils and/or undesired microorganisms at the locus.
By xe2x80x9ccombatxe2x80x9d we mean that the composition of the second aspect can be used to remove and/or break down malodour compounds and/or soils and/or microorganisms at the locus and/or it can prevent malodours and/or soils and/or microorganisms from building up at the locus. The term xe2x80x9cmicroorganismxe2x80x9d is used in this specification to denote any microscopic organism which is combatted; but especially a bacterium. Also of interest, however, as microorganisms which are prospectively combatted by compositions of the invention, are viruses and fungi, in particular yeasts. One pathogenic microorganism which is of particular interest as demonstrating the efficacy of the compositions of the present invention is the bacterium Staphylococcus aureus.
Said composition of the second aspect includes deodorising compositions and anti-allergenic compositions. For example the compositions may have a deodorising effect, by breaking down odoriferous compounds, as deposits and/or as airborne compounds. For such uses the compositions may be applied to surfaces in the appropriate location or may be used in room sprays.
By means of the present invention a residue or layer of photocatalytic material can be provided at a locus, for example on a surface whereby soils and/or undesired microorganisms deposited on the residue or layer or soils or undesired microorganisms which are present on the surface prior to deposition of the residue or layer are subject to a photocatalytic or other photochemical oxidation, reduction, free radical or other photochemical reaction effective to break down, xe2x80x9cburn awayxe2x80x9d or otherwise decompose the soils or undesired microorganisms or at least major components thereof; and/or to weaken their contact with the surface. Consequently it may be said that the cleaning process continues after the conventional act of removal of the soil or undesired microorganisms is completed.
As noted above soils may contain allergenic material which is decomposed or otherwise degraded by means of the present invention. Of particular interest is the use of the compositions of the invention in combating allergenic soils associated with house dust mites.
It is believed that the faeces of two particular house dust mite species, Dermatophagoides farinae (known as Der-f) and Dermatophagoides pteronyssinus (known as Der-p) trigger the immune responses of the body, thereby giving rise to well known allergenic responses.
A review of this is given in Experimental and Applied Acarology, 10 (1991) p. 167-186 in an article entitled xe2x80x9cHouse dust-mite allergenxe2x80x9d, a review by L. G. Arlian.
Both the Der-f and Der-p species are found throughout the world. In some areas, Der-f will be the sole Dermatophagoides species. In other areas Der-p will be the sole species. In still other areas, the two species are both present through, generally, one or the other will predominate.
Using the photocatalytic material, a decomposition reaction undergone by a malodour compound or a soil may involve photo-induced oxidation and/or photo-induced reduction reactions with organic or inorganic components of the malodour compound or soil. These reactions may in turn result in the production of free radicals which are effective in breaking down organic matter in the malodour compound or soil. These reactions may also provide an ongoing benefit after the initial deodorising or cleaning process has been completed.
One suitable photocatalytic material is titania and a possible mode of action using titania is now described, and shown schematically below. Whilst we are not bound by any scientific theory, in this suggested mode of action, incident light of appropriate energy can promote an electron from a valence band of the titania to a conductance band. There is then an electron (exe2x88x92) in the conductance band and a hole (h+) in the valence band. Both the electron and the hole may migrate to the surface of the titania particle and interact with oxygen and water to produce radical species. These radical species may then generate free radical decomposition reactions in the organic soil which may ultimately generate carbon dioxide if the free radical reaction continues to its conclusion. It is believed that the sensitiser is able to absorb light from the visible or ultra violet or infra-red (preferably the visible) region which causes an excitation of the sensitiser. Electrons are then emitted as the sensitiser decays or decomposes from the excited state, and these electrons are transferred to the conductance band of the photocatalytic material, such as titania. 
The photocatalytic material in the compositions of the present invention preferably includes titania, zinc oxide or a combination of the two, and is preferably present in an amount of from 0.01% to 20%, especially 0.2% to 3%, and most preferably 0.3 to 1%, by weight of the composition. Titania is preferred as the sole photocatalytic material. Most preferred is titania in anatase form, although the rutile form may be highly effective.
Preferably the photocatalytic material is imperceptible or almost imperceptible to the user after application. Preferably, the photocatalytic material used in the present invention is of a microscopic particle size. The microscopic particle size also assists in achieving a uniform dispersion throughout the formulation and in maximising the efficiency of the photocatalytic reaction. Suitably the photocatalytic material has a mean particle size (diameter) of at least 5 nm, preferably at least 10 nm, most preferably at least 15 nm. Suitably the photocatalytic material has a mean particle size of less than 200 nm, preferably less than 100 nm. One especially preferred class of titania particles, made using the Woodhead process described later, has a mean particle size in the range 5-30 nm. Another preferred class, being titania commercially available from Millenium Inorganic Chemicals, has a mean particle size in the range 30-100 nm.
The photocatalytic material may be doped with an additional element which has the effect of reducing the energy required to promote an electron of the photocatalytic material to the conductance band, leaving the corresponding hole in the valence band.
Preferably, the sensitiser is present in an amount up to 1%, more preferably up to 0.1%, still more preferably up to 0.02%, and yet more preferably up to 0.01%. Preferably it is present in an amount from 0.00001%, more preferably from 0.0001%.
In this invention the sensitiser preferably absorbs radiation of wavelength which is in the band 200-1200 nm, preferably 400-800 nm. Its absorbency peak within these bands may be narrow. Thus, it may typically absorb within a sub-band 50-200 nm in width.
There are many sensitisers which will improve the efficacy of the photocatalytic material. Examples may include cationic, anionic, nonionic and amphoteric dyes. Cationic dyes are one preferred class. Examples include the sensitisers described in U.S. Pat. No. 5,200,292. Thus, suitable sensitisers include cationic dye/anionic borate dye complexes represented by the general formula (I): 
wherein D+ represents a cationic dye; and R1, R2, R3 and R4, which may be the same or different, each represents an unsubstituted or substituted alkyl group, an unsubstituted or substituted aryl group, an unsubstituted or substituted aralkyl group, an unsubstituted or substituted alkenyl group, an unsubstituted or substituted alkynyl group, an unsubstituted or substituted alicyclic group, or an unsubstituted or substituted heterocyclic group.
Examples of the cationic sensitisers which can be used in the present invention include cyanine dyes and dyes comprising a cation portion such as a quaternary ammonium ion covalently bonded to other neutral sensitiser structures via a bonding group.
Cationic dye/borate anion complexes are known in the art. Examples of methods for the preparation of these complexes and the use of these complexes in an image formation system are described in U.S. Pat. Nos. 3,567,453, 4,307,182, 4,343,891, 4,447,521, 4,450,227, and 5,200,292.
For example the cationic dye/borate anion complex which can be used in the present invention can be prepared by allowing a borate salt and a sensitiser to react in a known counter ion exchange process. This process is further disclosed in Hishiki, Y., Repts. Sci-Research Inst. (1953), 29, pp 72 to 79. Examples of useful borate salts include sodium salts such as sodium tetraphenyl borate, sodium triphenyl butyl borate and sodium trianisyl butyl borate, and ammonium salts such as tetraethyl ammonium tetraphenyl borate.
Examples of useful cationic dyes to be used in the present invention include photo-reducible cationic dyes capable of forming a complex which is stable in a dark place with a borate anion, such as cationic methine, polymethine, triarylmethane, indoline, thiazine, xanthene, oxazine and acridine dyes. More particularly, these dyes are cationic, carbocyanine, hemicyanine, rhodamine and azomethine dyes.
Cationic cyanine dyes disclosed in U.S. Pat. No. 3,495,987 and U.S. Pat. No. 5,200,292 are believed to be useful in the present invention.
Specific examples of dyes believed useful include methylene blue, safarine O, malachite green, cyanine dyes of the general formula (II) below and rhodamine dyes of the general formula (III) below (e.g., Rhodamine B or Rhodamine 6G). 
wherein n represents 0 or an integer of 1 to 3; R represents an alkyl group; and Y represents CHxe2x80x94CH, Nxe2x80x94CH3, C(CH3)2, O, S or Se.
In the general formula (II), R is preferably a lower alkyl group (preferably having 1 to 8 carbon atoms) or an alkyl group (preferably having 1 to 5 carbon atoms) substituted by at least one of a carboxyl group, a sulfo group (itself optionally substituted by, for example, a hydroxy group or a halogen atom), a hydroxyl group, a halogen atom, an alkoxy group having 1 to 4 carbon atoms (itself optionally substituted by, for example, one or more alkoxy groups having 1 to 4 carbon atoms or sulfoalkoxy groups having 1 to 4 carbon atoms), a phenyl group or a substituted phenyl, for example, xcex2-sulfoethyl, xcex3-sulfopropyl, xcex3-sulfobutyl, xcex4-sulfobutyl, 2-[2-(3-sulfopropoxy)ethoxy]ethyl, 2-hydroxysulfopropyl, 2-chlorosulfopropyl, 2-methoxyethyl, 2-hydroxyethyl, carboxymethyl, 2-carboxyethyl, 2,2,3,3xe2x80x2-tetrafluoropropyl, 3,3,3-trifluoropropyl or trifluoroethyl. 
wherein Rxe2x80x2 and Rxe2x80x3 each represents a hydrogen atom, an alkyl group (preferably having 1 to 6 carbon atoms), an aryl group or combination thereof, for example, methyl, ethyl, propyl, butyl, penryl, hexyl, phenyl or benzyl.
The borate anion used in the present invention is so designed that a borate radical produced by the transfer of an electron to a sensitiser upon exposure to light easily dissociates into a radical as follows:
xe2x80x83BR4xe2x80x2xe2x80x3xe2x86x92BR3xe2x80x2xe2x80x3+Rxe2x80x2xe2x80x3
For example, triphenylbutyl borate anion and trianisylbutyl borate anion easily dissociate into triphenyl boran or trianisyl boran and a butyl radical. Thus, these anions are particularly preferred anions. On the other hand, tetrabutyl borate anion does not easily dissociate probably because a tetrabutyl borate radical produced therefrom is so unstable that it accepts an electron from a sensitiser. Similarly, tetraphenyl borate anion functions poorly because it cannot easily produce a phenyl radical.
In the borate anion represented by the general formula (I), one or two of R1, R2, R3 and R4 are preferably alkyl groups. R1, R2, R3 and R4 each may contain 20 or less carbon atoms, preferably 1 to 7 carbon atoms. A preferable combination of R1, R2, R3 and R4 is one or more alkyl groups and one or more aryl groups, or one or more alkyl groups and one or more aralkyl groups. Particularly, a combination of three aryl groups and one alkyl group is most preferred.
Typical examples of alkyl groups represented by R1, R2, R3 and R4 include methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl and stearyl groups. Such an alkyl group may be substituted by one or more halogen atoms, one or more cyano, acyloxy, acyl, alkoxy or hydroxy groups.
Typical examples of aryl groups represented by R1, R2, R3 and R4 include phenyl, naphthyl, and substituted aryl groups such as anisyl, and alkaryl such as methyl phenyl and dimethyl phenyl.
Typical examples of aralkyl groups represented by R1, R2, R3 and R4 include benzyl and phenethyl groups. Typical examples of alicyclic groups represented by R1, R2, R3 and R4 include cyclobutyl, cyclopentyl and cyclohexyl groups. Examples of unsubstituted alkynyl groups represented by R1, R2, R3 and R4 include propynyl and ethynyl groups. Examples of substituted alkynyl groups represented by R1, R2, R3 and R4 include a 3-chloropropynyl group. Examples of unsubstituted alkenyl groups represented by R1, R2, R3 and R4 include propenyl and vinyl groups. Examples of substituted alkenyl groups represented by R1, R2, R3 and R4 include 3-chloropropenyl and 2-chloroethenyl groups. Examples of unsubstituted heterocyclic groups represented by R1, R2, R3 and R4 include 3-thiophenyl and 4-pyridinyl groups. Examples of substituted heterocyclic groups represented by R1, R2, R3 and R4 include a 4-methyl-3-thiophenyl group.
Useful cationic dye/borate anion complexes may empirically confirmed. A combination of a cationic dye and a borate anion having a useful possibility can be fixed by Weller""s equation (Rehm, D. and Weller, A., Isr. J. Chem., (1970), 8, pages 259 to 271). The equation can be simplified as follows:
xcex94G=Eoxxe2x88x92Eredxe2x88x92Ekv
wherein xcex94G represents the change in Gibbs"" free energy; Eox represents the oxidation potential of borate anion BR4xe2x80x2xe2x80x3-; Ered represents the reduction potential of an anionic sensitiser; and Ekv represents the energy of light used for the excitation of the sensitiser.
It is believed that a useful complex has a negative free energy change. Similarly, the difference in the reduction potential of the sensitiser and the oxidation potential of borate must be negative with respect to a complex which is stable in a dark place.
Namely,
Eoxxe2x88x92Ered greater than 0
As previously mentioned, this is a simplified equation and thus does not absolutely predict if a complex is useful in the present invention. There are many other factors which affect such a decision. One of these factors is the effect of the use of a monomer on a complex. It is known that if Weller""s equation gives an excessive negative value, there can be some deviation from the equation. Thus, this equation is only a first approximation.
Particular examples of cationic dye/borate anion complexes believed useful in the present invention will be shown hereafter together with their peak absorbency wavelength, in nanometers (xcexmax).
Other preferred sensitisers include the ruthenium sensitisers described in J.Am.Chem. Soc., Vol. 122, No. 12, 2000, pp. 2840-2849. These have three pairs of carboxylated bipyridyl groups complexed to a ruthenium (II) or ruthenium (III) atom. Two such complexes may be coupled together to make a polypyridine dyad, preferably an Ru(II)-Ru(III) polypyridine dyad.
Examples of preferred ruthenium sensitisers thus include the compounds:
ruthenium (III) bis-(4,4xe2x80x2-dicarboxyl-2,2xe2x80x2-bipyridine)-(1,2-bis[4-(4xe2x80x2-methyl-2,2xe2x80x2-bypyridyl)]ethane)-ruthenium(II) bis-(4,7-dimethyl-1,10-phenanthroline)
ruthenium (III) bis-(4,4xe2x80x2-dicarboxyl-2,2xe2x80x2-bipyridine)-(1,2-bis[4-(4xe2x80x2-methyl-2,2xe2x80x2-bypyridyl)]ethane)-ruthenium(II) bis-(2,2xe2x80x2-bipyridine)
ruthenium (II) bis-(4,4xe2x80x2-dicarboxyl-2,2xe2x80x2-bipyridine)-(4,4xe2x80x2-dimethyl-2,2xe2x80x2-bipyridine)
ruthenium (II) tris-(4,4xe2x80x2-dicarboxyl-2,2xe2x80x2-bipyridine)
Other classes of sensitisers of interest for use with a photocatalytic material in the present invention the materials described in GB 1408144. They include eosin, rose bengal, fluorescein, chlorophyll, metal-free porphyrin, sulphonated phthalocyanine and sulphonated zinc phthalocyanine.
Other classes of sensitisers of interest for use with a photocatalytic material in the present invention include organosilicon (IV) phthalocyanines and naphthocyanines having Q-band absorption maxima at wavelengths greater than 660 nm, having the formula 
wherein R1, R2, R3, R4, R5 and R6 units are each independently selected from the group consisting of:
a) hydrogen;
b) halogen;
c) hydroxyl;
d) cyano;
e) nitrilo;
f) oximino;
g) C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
h) halogen substituted C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
i) polyhydroxyl substituted C3-C22 alkyl;
j) C1-C22 alkoxy;
k) branched alkoxy having the formula: 
xe2x80x83wherein B is hydrogen, hydroxyl, C1-C30 alkyl, C1-C30 alkoxy, xe2x80x94CO2H, xe2x80x94CH2CO2H, xe2x80x94SO3xe2x88x92M+, xe2x80x94OSO3xe2x88x92M+, xe2x80x94PO32xe2x88x92M, xe2x80x94OPO32xe2x88x92M, or mixtures thereof, M is a water soluble cation in sufficient amount to satisfy charge balance; x is 0 or 1, each y independently has the value from 0 to 6, each z independently has the value from 0 to 100;
l) substituted or unsubstituted aryl;
m) substituted or unsubstituted alkylenearyl;
n) substituted or unsubstituted aryloxy;
o) substituted or unsubstituted oxyalkylenearyl;
p) substituted or unsubstituted alkyleneoxyaryl;
q) C1-C22 thioalkyl, C4-C22 branched thioalkyl, or mixtures thereof;
r) an ester of the formula xe2x80x94CO2R10 wherein R10 comprises:
i) C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C2- branched alkenyl, or mixtures thereof;
ii) halogen substituted C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
iii) polyhydroxyl substituted C3-C22 alkyl;
iv) C3-C22 glycol;
v) C1-C22 alkoxy;
vi) C4-C22 branched alkoxy;
vii) substituted or unsubstituted aryl;
viii) substituted or unsubstituted alkylaryl;
ix) substituted or unsubstituted aryloxy;
x) substituted or unsubstituted alkoxyaryl;
xi) substituted or unsubstituted alkyleneoxyaryl; or mixtures thereof,
s) an amino unit of the formula:
xe2x80x83xe2x80x94NR11R12
xe2x80x83wherein R11 and R12 comprises C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
t) an alkylethyleneoxy unit of the formula:
xe2x80x94(A)vxe2x80x94(CH2)y(OCH2OCH2)xZ
xe2x80x83wherein Z comprises:
i) hydrogen;
ii) hydroxyl;
iii) xe2x80x94CO2H;
iv) xe2x80x94SO3xe2x88x92M+;
v) xe2x80x94OSO3xe2x88x92M+;
vi) C3-C6 alkoxy;
vii) substituted or unsubstituted aryl;
viii) substituted or unsubstituted aryloxy;
ix) alkyleneamino; or mixtures thereof;
A units comprise nitrogen or oxygen, M is a water soluble cation, v is 0 or 1, x is from 0 to 100, y is from 0 to 12;
u) and mixtures thereof; axial R units wherein each R is independently selected from the group consisting of:
a) hydrogen;
b) cyano;
c) nitrilo;
d) oximino;
e) C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
f) halogen substituted C1-C22alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
g) polyhydroxyl substituted C3-C22 alkyl;
h) branched alkoxy having the formula: 
xe2x80x83wherein R is hydrogen, hydroxyl, C1-C30 alkyl, C1-C30 alkoxy, xe2x80x94CO2H, xe2x80x94CH2xe2x80x94CO2H, xe2x80x94SO3xe2x88x92M+, xe2x80x94OSO3xe2x88x92M+, xe2x80x94PO32xe2x88x92M, xe2x80x94OPO32xe2x88x92M, or mixtures thereof; M is a water soluble cation in sufficient amount to satisfy charge balance; x is 0 or 1, each y independently has the value from 0 to 6, each z independently has the value from 0 to 100;
i) an alkyleneamino unit of the formula: 
xe2x80x83wherein R11 and R12 comprises C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
R16 comprises:
i) hydrogen;
ii) C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
A units comprise nitrogen or oxygen; X comprises chlorine, bromine, iodine or other water soluble anion, v is 0 or 1, u is from 0 to 22;
j) an amino unit is of the formula:
xe2x80x94NR11R12
xe2x80x83wherein R11 and R12 comprises C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
k) carboxylate of the formula: 
xe2x80x83wherein R10 comprises:
i) C4-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C1-C22 branched alkenyl, or mixtures thereof;
ii) halogen substituted C1-C22 alkyl, C4-C22 branched alkyl, C2-C22 alkenyl, C4-C22 branched alkenyl, or mixtures thereof;
iii) poly-hydroxyl substituted C3-C22 alkyl;
iv) C3-C22 glycol;
v) C1-C22 alkoxy;
vi) C4-C22 branched alkoxy;
vii) substituted or unsubstituted aryl;
viii) substituted or unsubstituted alkylaryl;
ix) substituted or unsubstituted aryloxy;
x) substituted or unsubstituted alkoxyaryl;
xi) substituted or unsubstituted alkyleneoxyaryl;
xii) alkyleneamino, or mixtures thereof;
l) and mixtures thereof.
Preferably in phthalocyanines (I above) each moiety R1-R4 is independently selected from hydrogen and C1-4 alkoxy, for example methoxy.
Preferably in the naphthocyanine (II above) each moiety R1-R6 is independently selected from hydrogen and halogen.
Preferably in phthalocyanine and naphthocyanine compounds the moieties R bonded to the central silicon atoms are polyhydroxyl substituted C3-22 alkylene moieties, preferably polyglycols of formula xe2x80x94(CHOH)nCH2OH, where n is 2-21, preferably 2-6, or branched alkoxy groups having the formula 
where B is hydrogen, hydroxyl, C1-C30 alkyl, C1-C30 alkoxy, xe2x80x94CO2H, xe2x80x94CH2CO2H, xe2x80x94SO3xe2x88x92M+, xe2x80x94OSO3xe2x88x92M+, xe2x80x94PO32xe2x88x92M, xe2x80x94OPO32xe2x88x92M, and mixtures thereof; M is a water soluble cation in sufficient amount to satisfy charge balance; x is 0 or 1, each y independently has the value from 0 to 6, preferably from 0 to 6; each z independently has the value from 0 to 100, preferably from 0 to about 10, more preferably from 0 to about 3.
Further information on these sensitisers may be found in U.S. Pat. No. 5,916,481, the contents of which are incorporated herein by reference.
Further information about useful sensitisers is found in WO 98/32829. The sensitisers described therein could be used in the present invention, and the descriptions thereof are preferably incorporated herein by reference. Thus, they may suitably have the formula: 
wherein M is a photoactive metal or non-metal having a valence greater than 3, rings A, B. C and D are aromatic rings, each of said rings being independently selected from the group consisting of benzene, 1,2-naphthalene, 2,3-naphthalene, anthracene, phenanthrene, and mixtures thereof.
Suitably rings A, B, C, and D are each independently:
i) a benzene ring unit, a 2,3-naphthylene ring unit, a 1,2-naphthylene ring unit, an anthracene ring unit or a phenenthene ring unit, each such ring unit being fused to the pyrrole ring shown above, and each ring unit being substituted, possible substituents being as defined in WO 98/32829, or, preferably, unsubstituted.
Disclosures of similar sensitisers are given in WO 98/32826, the contents of which are also incorporated herein by reference.
In a third aspect of the present invention there is also provided a composition which comprises:
a) a photocatalytic material able to combat malodours and/or soils and/or undesired microorganisms or a precursor to such a photocatalytic material; and
b) a sensitiser which is capable of absorbing radiation of a first wavelength from visible light, for example room lighting or daylight, consequently adopting an excited state, and relaxing from that excited state by ejecting an electron, thereby enhancing the efficacy of the photocatalytic material against the malodours and/or soils and/or undesired microorganisms.
The compositions of the present invention may be provided in any appropriate dry or wet form such as, for example, a liquid, cream, mousse, emulsion, microemulsion, gel, powder or block. They may be dispensed in conventional manner directly from a bottle or by means of, for example, a pump or a trigger spray or roller or an aerosol or, in the case of a powder, by a puffer or sprinkler. Also, they could be applied to a surface by a brush, dispensing stick, impregnated woven or non-woven cloth, or sponge.
Liquid compositions are especially preferred, especially aqueous liquid compositions. Aqueous liquid compositions can be emulsions, including microemulsions, and/or may contain solvents which solubilise those sensitisers which do not dissolve in a water phase. Liquid compositions could be supplied ready-for-use or dilutable.
Whilst the person skilled in the art will be able to prepare aqueous and non-aqueous liquid formulations tailored to the above dispensing forms, the compositions of the present invention generally comprise not more than 99.7%, preferably 75% to 95% water, and cationic, anionic, nonionic or amphoteric surfactants, or compatible combinations thereof, in an amount of 0.05% to 80%, typically 0.5% to 10%. Surfactants should be selected having regard to the nature of the composition, in particular the photocatalytic agent or the precursor therefor, to ensure in-pack stability. In general, anionic surfactants are not suitable for incorporation in acidic compositions, especially those containing titania. In general cationic surfactants are not suitable for incorporation in alkaline compositions, especially those containing titania. Nonionic surfactants are especially preferred in compositions of the present invention.
Examples of nonionic surfactants which may be employed in the composition include those which are water soluble or water miscible and include but are not limited to one or more of the following: amine oxides, block copolymers, alkoxylated alkanolamides, alkoxylated alcohols, alkoxylated alkyl phenols, and sorbitan esters, for example sorbitan mono oleate. In each case the respective alkyl group is preferably a fatty alkyl group, suitably having from 7 to 24 carbon atoms, preferably 8 to 16, and may be branched or, more preferably, linear. Alkoxylate chains may be propoxylate chains, mixed ethoxylate/propoxylate chains or, most preferably, ethoxylate chains. Good examples include linear fatty alcohol ethoxylates (e.g. NEODOL, from Shell) and secondary fatty alcohol ethoxylates (e.g. TERGITOL, from Union Carbide). Other examples include alkoxylated octyl and nonyl phenols (e.g. IGEPAL, from Rhone-Poulenc).
Examples of cationic surfactants which may be used in the present invention include quaternary ammonium compounds and salts thereof, including quaternary ammonium compounds which also have germicidal activity and which may be characterized by the general structural formula: 
when at least one of R1, R2, R3 and R4 is a hydrophobic, aliphatic, aryl aliphatic or aliphatic aryl group containing from 6 to 26 carbon atoms, and the entire cationic portion of the molecule has a molecular weight of at least 165. The hydrophobic groups may be long-chain alkyl, long-chain alkoxy aryl, long-chain alkyl aryl, halogen-substituted long-chain alkyl aryl, long-chain alkyl phenoxy alkyl or aryl alkyl. The remaining groups on the nitrogen atoms, other than the hydrophobic radicals, are generally hydrocarbon groups usually containing a total of no more than 12 carbon atoms. The radicals R1, R2, R3 and R4 may be straight chain or may be branched, but are preferably straight chain, and may include one or more amide or ester linkages. The radical X may be any salt-forming anionic radical.
Examples of quaternary ammonium salts within the above description include the alkyl ammonium halides such as cetyl trimethyl ammonium bromide, alkyl aryl ammonium halides such as octadecyl dimethyl benzyl ammonium bromide, and N-alkyl pyridinium halides such as N-cetyl pyridinium bromide. Other suitable types of quaternary ammonium salts include those in which the molecule contains either amide or ester linkages, such as octyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride and N-laurylcocoaminoformylmethyl)-pyridinium chloride. Other effective types of quaternary ammonium compounds which are useful as germicides includes those in which the hydrophobic radical is characterized by a substituted aromatic nucleus as in the case of lauryloxyphenyltrimethyl ammonium chloride, cetylaminophenyltrimethyl ammonium methosulphate, dodecylphenyltrimethyl ammonium methosulphate, dodecylphenyltrimethyl ammonium chloride and chlorinated dodecylphenyltrimethyl ammonium chloride.
Preferred quaternary ammonium compounds which act as germicides and which are useful in the present invention include those which have the structural formula: 
wherein R2 and R3 are the same or different C8-C12alkyl, or R2 is C12-C16alkyl, C8-C18alkylethoxy, C8-C18-alkyl-phenolethoxy and R2 is benzyl, and X is a halide, for example chloride, bromide or iodide, or methosulphate. The alkyl groups R2 and R3 may be straight chain or branched, but are preferably substantially linear.
A mixture of two or more surface active agents may also be used. Other known surface active agents not particularised above may also be used in some compositions; especially when one of them is a nonionic surfactant. Surface active agents in general are described in McCutcheon""s Detergents and Emulsifiers, North American Edition, 1982; Kirk-Othmer, Encyclopaedia of Chemical Technology, 3rd Ed., Vol. 22, pp 346-387.
Grease cutting, adhesion promoting or other solvents may also be included generally in amounts of not more than 99%, typically not more than 50%. Examples include glycols and glycol ethers.
Preferred ingredients of the composition are C1-6 alkanols, for example ethanol and isopropanol. These may aid adhesion, promote soil removal and appear, surprisingly, to enhance photocatalytic activity. When present they preferably constitute 1-10%, preferably 2-5% of the composition, by weight.
Other ingredients of the compositions may include dispersing agents, suspending agents, colorants, fragrances, polishes, sequestrants, fabric softening agents, optical brighteners, laundry anti-fade agents, enzymes, thickeners, preservatives, bleaches, bleach activators, waxes, stabilising agents, propellants and further material(s) to combat undesired microorganisms. In particular variations of liquid compositions of the invention, some or all of the ingredients may be of high volatility whereby a residue of photocatalytic material can be left behind on a surface in a controlled manner.
Suitable dispersing agents may include hydroxyethyl cellulose, polyvinyl alcohol, polyvinyl acetate and ethylene oxide-propylene oxide block copolymers. Such agents may aid in-pack stability and promote good surface contact, on application.
Suitable adhesion promoters may include materials selected from polyvinyl alcohols, polyacrylic acids, ethylene oxide-propylene oxide block copolymers, hydroxyethyl celluloses, protein polymers and polysaccharide polymers. Preferred adhesion promoters may include polyvinyl alcohols, alginates, gum arabic, and pectin.
Liquid compositions of the invention, ready for use, may be of pH in the range 1 to 13, preferably 2 to 12, most preferably 3 to 11. The pH may not be the same as that of as-supplied liquid compositions, because the latter may be diluted.
In one embodiment the composition is a bleaching composition containing a peroxygen compound, for example hydrogen peroxide or a generator thereof, or peracetic acid or persuccinic acid.
The components of the composition should be selected, and/or the composition formulated, such that the composition is stable for a sufficient period, without components being degraded or rendered unstable by the photocatalytic material and the sensitiser. Alternatively, certain components could be kept apart from other components, for example in a twin pack formulation. Preferably the compositions are packaged for sale in containers which shield the compositions from electromagnetic radiation of wavelength which would promote its photocatalytic action. All such measures are within the ordinary competence of persons skilled in the art.
Liquid compositions preferably have suitable rheology to suspend particles and/or to inhibit run off from upright surfaces, on application. To this end liquid compositions may be thixotropic, and preferably exhibit shear thinning with a suitable, preferably low, yield point.
Preferred compositions of the invention are colloidal suspensions of photocatalytic particles, more preferably transition metal oxide particles, and most preferably titania particles.
Preferred colloidal suspensions of titania particles for use in the present invention are prepared by steps of hydrolysis of titanium tetrachloride in ammonium hydroxide, washing the precipitate thus formed, decreasing the pH to 3.3 by addition of a mineral acid, preferably nitric acid, washing until the conductivity drops below 500 xcexcS, and peptisation by addition of a mineral acid, preferably nitric acid, either at room temperature for 7 days or at 60-70xc2x0 C. for 30-90 minutes. The resultant colloidal suspension of titania typically has a titania concentration of about 10 g/l and a mean particle size of about 20 nm. This method is known as the Woodhead method, after the inventor and patentee thereof.
Alternative colloidal suspensions of titania particles for use in the present invention may be prepared by the xe2x80x9cisopropoxidexe2x80x9d method. This method involves the steps of hydrolysis of titanium isopropoxide, suitably in ammonium hydroxide, washing the precipitate thus formed, filtration, and peptisation by addition of a mineral acid, preferably nitric acid, either at room temperature for 7 days or at 60-70xc2x0 C. for 30-90 minutes. The resultant colloidal suspension of titania typically has a titania concentration of 25-30g/l and a mean particle size of about 20 nm, when the peptisation is at ambient temperature. When the peptisation is at the elevated temperature, the resultant colloidal suspension typically has a titania concentration in excess of 100 g/l and a mean particle size of about 90-100 nm, but with a wide particle size distribution.
Further alternative colloidal suspensions of titania particles for use in the present invention may be prepared by the Kormann method. In this method titanium tetrachloride is hydrolysed at 0xc2x0 C. under a nitrogen blanket. Dialysis is carried out for 3-12 hours to remove undesired by-products of the hydrolysis. The resulting titania suspension is dried using a rotary evaporator, aided by a water bath held at 30xc2x0 C. The resulting solid is re-suspended in deionised water. No peptisation step is required. The resulting colloidal suspension of titania typically has a titania concentration of about 1 g/l and a mean particle size in the range 30-70 nm.
In accordance with a fourth aspect of the present invention there is provided a method of cleaning or sanitising a surface, the method comprising the steps of contacting the surface with a composition of the invention as defined above thereby depositing a residue of the photocatalytic material on the surface, and allowing the photocatalytic material to combat soils or undesired microorganisms present on or subsequently deposited on the surface.
In the case of soils the combating may be by catalysing or effecting an oxidation, reduction or other decomposition of the soils.
The method is suitably carried out with the surface and the composition at ambient temperature and without any subsequent heat treatment.
The method is suitably carried out under visible light of intensity at least 5,000 lux. Preferably the method is carried out under ambient light conditions, for example daylight and/or under room lighting.
Acidic conditions may be favoured for methods of cleaning or sanitising bathrooms and lavatories.
Alkaline conditions may be favoured for methods of cleaning or sanitising laundry and kitchen environments.
Neutral or near-neutral conditions may be favoured for methods of treating delicate fabrics and surfaces (for example marble, and certain painted surfaces).
The skilled person may consult readily available zeta potential plots for chosen photocatalytic materials in order to ascertain available and optimal ranges of surfactants. Furthermore, the skilled person may use dispersing agents to allow co-formulation of materials which may otherwise be incompatible.
The colloidal and interfacial nature of the photocatalytic material will determine the nature of the sensitisers, surfactants and other materials which can be employed to good effect, having regard to in-pack stability, surface coverage and adhesion and photocatalytic activity. In the case of any doubt, of course, trial and error can be used. However, by way of guidance we can make the following general statements.
Preferred acidic titania-containing compositions include a cationic and/or a nonionic surfactant; and preferably no anionic surfactant. A nonionic surfactant is in all cases a preferred constituent.
Preferred alkaline titania-containing compositions include an anionic and/or a nonionic surfactant; and preferably no cationic surfactant (in contrast, with certain mildly alkaline compositions containing zinc oxide cationic surfactants may also be used). A nonionic surfactant is in all cases a preferred constituent.
Neutral or near-neutral compositions may contain a surfactant of any type, and preferably include a nonionic surfactant.
The surfaces treated in the method may be hard surfaces, for example surfaces of wooden objects, tiles, sanitaryware, painted objects, panels, kitchen surfaces, worktops, walls, floors, windows, mirrors, shower cubicles and shower curtains, and cars. The hard surfaces may be the surfaces of outdoor garden structures, for example greenhouses, outdoor furniture, patios and paths.
The surfaces treated in the method may be fibrous surfaces, for example clothes, furnishing fabrics and carpets.
As mentioned above and as is evidenced from the foregoing description and following examples our main interest is in providing a consumable surface cleaning composition which has, to paraphrase, a keep-clean or self-clean action. However, other compositions having a photocatalytic material or a precursor to the photocatalytic material and a sensitiser in admixture are included in the scope of the invention. Such compositions may, for example, be permanently secured to the surface of a substrate, for example of ceramic, glass or plastics. Securement may be by chemical bonding and/or a quasi-mechanical process, such as sputtering; or may be incorporated in an article, for example of ceramic, glass or plastics, during its manufacture. For example, the composition could be compounded with a plastics material prior to its moulding or extrusion. Also covered are compositions to be added to water, to sanitise and/or decolorise it and/or to combat soils and/or microorganisms on surfaces in contact with the water.
The following examples are illustrative of compositions according to the invention in the form of a liquid. They may all contain sensitisers, colorants, fragrances and preservatives, preferably at concentrations not more than 1% each, with the balance of the formulations being titania and water.
All percentages in this specification are expressed in weight of component per total weight of composition (that is w/w) unless otherwise stated.
The invention will now be further described by way of example, with reference to the following non-limiting embodiments.
Unless otherwise stated the examples now described employ the sensitiser ruthenium (II) tris-(4,4xe2x80x2-dicarboxyl-2,2xe2x80x2-bipyridine) mentioned above, hereinafter called xe2x80x9cSensitiser Axe2x80x9d, and having the CAS number CAS 97333-46-5. When acid blue colorant is mentioned it is the water soluble colorant known as acid blue F.Y.D.